1. The expression of the gene for retinol-binding protein in choroid plexus from rats, mice, sheep and cattle is demonstrated by Northern analysis and reverse transcription coupled with polymerase chain reaction. 2. The content of retinol-binding protein mRNA in total RNA from choroid plexus of ruminants was higher than that for RNA from any other extrahepatic tissues of adult animals reported so far. 3. The ratios of retinol-binding protein mRNA levels in choroid plexus RNA to those in liver RNA varied greatly among rodents, ruminants and carnivores.